A cardiac PET scan uses positron emission tomography (PET) imaging technology to examine vascular blood flow and cardiac function and to diagnose related disorders. Physicians may also use this noninvasive medical imaging device for diagnosing other medical conditions, including brain disorders and cancer. While magnetic resonance imaging (MRI) and computed tomography (CT) scans also provide images of anatomical structures, PET scanning displays physiological functional processes.
Physicians believe that PET scans provide more accurate information than conventional electrocardiograms and stress tests when attempting to diagnose heart disease. A doctors may require a cardiac PET scan if he suspects heart disease in patients who exhibit no visible symptoms of vascular flow deficit. The PET scan also provides diagnostic information when physicians suspect cardiac or vascular problems based on symptoms experienced during physical exertion or while at rest.
A patient undergoing a cardiac PET scan typically receives an intravenous (IV) injection of a radionucleotide chemical combined with glucose. Fluorodeoxyglucose, commonly referred to as FDG, is the radioactive tracing material most often used. FDG emits gamma rays, which the PET scanner detects as it revolves around the interior of the machine. The scanner relays the signals to a computer console, which displays the signals as an image.
Physicians evaluate the path of blood flow to the heart by observing the images produced by the cardiac PET scan. After receiving circulation images while the patient is calm and relaxed, physicians may require additional images following physical exercise or simulated exertion induced by medications such as dipyridamole. Diseased vasculature exhibits signs of decreased blood flow during physical activity because of stenosis.
Besides tracing blood flow patterns, cardiac PET scan images also illuminate the areas of the heart and vasculature that are not absorbing the glucose laden IV chemical. These locations are areas in which the tissue is damaged. The scans usually provide physicians with the information necessary to decide on a specific plan of treatment. Physicians can observe the effectiveness of lipid lowering agents or determine whether patients require surgical intervention, including bypass or transplant procedures.
As radiation is involved in the procedure, cardiac PET scans are not generally recommended for pregnant or lactating patients, and diabetic patients may receive special instructions concerning the glucose used in the injection. A period of abstinence from food and drink is required prior to the procedure. Unless otherwise instructed, however, water is usually allowed before the scan.